Pad assemblies for electrochemically assisted planarization

ABSTRACT

In one embodiment, a pad assembly for electro-processing a substrate is provided which includes a first conductive layer having a working surface to contact the substrate during a polishing process, an intermediate layer coupled to the first conductive layer, wherein the intermediate layer contains a plurality of perforations, channels, or combinations thereof, which have diameters within a range from about 0.5 mm to about 10 mm, and a second conductive layer coupled to the intermediate layer, wherein the second conductive layer has a plurality of independently electrically biasable zones and is configured to be coupled with a power delivery arrangement. The intermediate layer may contain a polymer material support disk, a backing layer, or combinations thereof. Generally, the first conductive layer, the second conductive layer, and the intermediate layer are adhered or secured together and removable as a unitary replaceable body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 11/425,339(APPM/007187.C2), filed Jun. 20, 2006, which is a continuation of U.S.Ser. No. 11/048,117 (APPM/007187.C1), filed Feb. 1, 2005, and issued asU.S. Pat. No. 7,070,475, which is a continuation of U.S. Ser. No.10/244,688 (APPM/007187), filed Sep. 16, 2002, and issued as U.S. Pat.No. 6,848,970, which are herein incorporated by reference in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to a method and apparatusfor planarizing a surface and, more particularly, to a method ofcontrolling the removal rate of material in electrochemically assistedchemical mechanical polishing (ECMP).

2. Background of the Related Art

Sub-quarter micron multi-level metallization is one of the keytechnologies for the next generation of ultra large-scale integration(ULSI). The multilevel interconnects that lie at the heart of thistechnology require planarization of interconnect features formed in highaspect ratio apertures, including contacts, vias, lines and otherfeatures. Reliable formation of these interconnect features is veryimportant to the success of ULSI and to the continued effort to increasecircuit density and quality on individual substrates and die.

In the fabrication of integrated circuits and other electronic devices,multiple layers of conducting, semiconducting, and dielectric materialsare deposited on or removed from a surface of a substrate. Thin layersof conducting, semiconducting, and dielectric materials may be depositedby a number of deposition techniques. Common deposition techniques inmodern processing include physical vapor deposition (PVD), also known assputtering, chemical vapor deposition (CVD), plasma-enhanced chemicalvapor deposition (PECVD), and electrochemical plating (ECP).

As layers of materials are sequentially deposited and removed, theuppermost surface of the substrate may become non-planar across itssurface and require planarization. “Planarizing” a surface, or“polishing” a surface, is a process where material is removed from thesurface of the substrate to form a generally even, planar surface.Planarization is useful in removing undesired surface topography andsurface defects, such as agglomerated materials, crystal lattice damage,scratches, and contaminated layers or materials. Planarization is alsouseful in forming features on a substrate by removing excess depositedmaterial used to fill the features and to provide an even surface forsubsequent levels of metallization and processing.

Chemical mechanical polishing (CMP) is a common technique used toplanarize substrates. CMP utilizes a chemical composition, typically aslurry or other fluid medium, for selective removal of material fromsubstrates. In conventional CMP techniques, a pad is moved relative tothe substrate by an external driving force. The CMP apparatus effectspolishing or rubbing movement between the surface of the substrate andthe polishing pad while dispersing a polishing composition to effectchemical activity and/or mechanical activity and consequential removalof material from the surface of the substrate.

One material increasingly utilized in integrated circuit fabrication iscopper due to its desirable electrical properties. However, copper hasits own special fabrication problems. Copper material is removed atdifferent removal rates along the different surface topography of thesubstrate surface, which makes effective removal of copper material fromthe substrate surface and planarity of the substrate surface difficultto achieve. For example, in one common non-uniformity pattern, coppermay be removed slower or faster at the edge and the center of thesubstrate when compared to an intermediate region of the substrate.

One solution for polishing a material such as copper is by usingelectrochemical mechanical polishing (ECMP) techniques. ECMP techniquesremove conductive material from a substrate surface by electrochemicaldissolution while concurrently polishing the substrate with reducedmechanical abrasion compared to conventional CMP processes. Theelectrochemical dissolution is performed by applying an electrical biasbetween an electrode and a substrate surface to remove conductivematerials from a substrate surface into a surrounding electrolyte.During electrochemical dissolution, the substrate typically is placed inmotion relative to a polishing pad to enhance the removal of materialfrom the surface of the substrate. In one embodiment of an ECMP system,the electrical bias is applied by a ring of conductive contacts inelectrical communication with the substrate surface in a substratesupport device, such as a substrate carrier head. In other ECMP systems,a bias is applied between an electrode and conductive pad that is incontact with the substrate surface. Unfortunately, these conventionalECMP systems fail to provide an ECMP method for polishing a substratethat delivers a uniform or predictable polishing rate (i.e., providing arate of material removal that can be controlled) across the surface ofthe substrate.

As a result, there is a need for a method of controlling the rate ofmaterial removal during ECMP.

SUMMARY OF THE INVENTION

Aspects of the invention generally provide a method for polishing amaterial layer using electrochemical deposition techniques,electrochemical dissolution techniques, polishing techniques, and/orcombinations thereof. In one aspect of the invention, the polishingmethod comprises separately applying a plurality of biases between amaterial layer and a plurality of zones of an electrode. The electrodeis generally a counter-electrode to the material layer and may comprisea plurality of conductive elements separated by a dielectric material.

The determination of the separate biases comprises determining a timethat at least one portion of the material layer is associated with eachof the zones of the counter-electrode. A polishing program used topolish the material layer encodes, for example, a sequence of relativepositions or relative motion between the counter-electrode and thematerial layer. Based upon the polishing program, an algorithm may beused to calculate a time period that a point on the material layer isassociated with each of the zones of the counter-electrode. The biasapplied to the zones of the counter-electrode may be selected to match adesired material removal profile. The desired removal profile may be,for example, a uniform profile, i.e., one that does not vary across thesurface to be polished. Alternatively, the removal profile may benon-uniform, so as to, for example, compensate for a substrate ormaterial layer that is uneven.

An optimization, such as a statistical optimization may be performed todetermine the optimal bias that should be associated with each zone ofthe counter-electrode. The optimization may be performed in order tosubstantially match the desired removal profile. The biases to beapplied to each zone of the counter-electrode may be selected using arelationship, such as a pre-determined relationship, between biasapplied to the material layer and the rate of material removal from thematerial layer.

In one aspect, a method is provided for processing a substrate includingdisposing a substrate containing a conductive material layer in aprocess apparatus comprising an electrode having a plurality of zones,moving the substrate relative to the plurality of zones with at leastone portion of the substrate passes through more than one zone of theplurality of zones, applying a bias to each of the plurality of zones,wherein the bias to each of the plurality of zones is modified by thetime that the at least one portion of the substrate layer is associatedwith more than one zone of the electrode, and removing conductivematerial from the conductive material layer.

In another aspect, a method is provided for processing a surface of amaterial layer including disposing a substrate containing a conductivematerial layer in a process apparatus comprising an electrode having aplurality of zones and a polishing pad having a plurality of zonescorresponding to the plurality of zones of the electrode, providingrelative motion between the polishing pad and the substrate, andseparately applying a plurality of biases between the plurality of zonesof the polishing pad and the plurality of zones of thecounter-electrode, wherein the plurality of biases removes conductivematerial from the conductive material layer at a rate that varies foreach of the plurality of zones of the polishing pad.

In another aspect, a method of polishing a surface of a material layercomprises providing relative motion between the material layer and acounter-electrode. The material layer is contacted with a polishing pad.During at least a portion of the relative motion, a plurality of biasesis separately applied between a material layer and a plurality of zonesof an electrode. The determination of the separate biases comprisesdetermining a distribution of times that at least one portion of thematerial layer is associated with each of the zones of thecounter-electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

A more particular description of the invention, briefly summarizedabove, may be had by reference to the embodiments thereof that areillustrated in the appended drawings. It is to be noted, however, thatthe appended drawings illustrate only typical embodiments of thisinvention and, therefore, are not to be considered limiting of itsscope, for the invention may admit to other equally effectiveembodiments.

FIG. 1A is a sectional view of one embodiment of a processing cell thatmay be used to practice embodiments described herein;

FIG. 1B is a sectional view of another embodiment of a processing cellthat may be used to practice embodiments described herein;

FIG. 2 is a bottom view of a counter-electrode that may be used topractice embodiments described herein;

FIG. 3 is a bottom perspective view of one embodiment of a polishing padthat may be used to practice embodiments described herein;

FIG. 4 is a sectional view of a process cell depicting a material layerbeing polished using embodiments of the invention described herein;

FIG. 5A-5B are top perspective views of a substrate having a materiallayer thereon, wherein the material layer may be polished in order todevelop a relationship between removal rate and applied bias, consistentwith embodiments described herein;

FIGS. 6A-6B depict two different removal rate profiles that may begenerated using embodiments described herein; and

FIG. 7 is a schematic, cross-sectional view of a material layer that maybe polished using embodiments described herein.

To facilitate understanding, identical reference numerals have beenused, wherever possible, to designate identical elements that are commonto the figures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1A depicts a sectional view of one embodiment of a process cell 100in which at least one or more processes including plating and polishing,or combinations thereof may be practiced. The process cell 100 may beused to practice electrochemical mechanical polishing (ECMP). ECMPshould be broadly construed and includes, but is not limited to,planarizing a substrate by the application of electrochemical activityor a combination of both electrochemical and mechanical activity toremove material from a substrate surface. The process cell 100 may beused to polish a substrate through an anodic dissolution process. In ananodic dissolution process, an anodic bias is applied to the substrate,directly or indirectly, resulting in removal of conductive material froma substrate surface into a surrounding electrolyte. The process cell 100may also be used to electrochemically deposit material onto a substrate.The electrochemical deposition may be concurrent with the application ofvarious forms of activity used to polish the substrate. The concurrentactivity may be electrochemical activity, mechanical activity, or acombination of both electrochemical and mechanical activity, such as areused in an electrochemical mechanical plating process (ECMPP).

The process cell 100 generally includes a basin assembly 152 and apolishing head 106. A substrate 104 may be retained in the basinassembly 152 during processing in a face-up (e.g., backside down)orientation. An electrolyte is flowed over a feature side 138 (surface)of the substrate 104 during processing. The polishing head 106 is placedin contact with the substrate 104, and the polishing head 106 and thesubstrate are moved relative to each other to provide a polishingmotion. The polishing motion generally comprises at least one motiondefined by an orbital, rotary, linear or curvilinear motion, orcombinations thereof, among other motions. The polishing motion may beachieved by moving either or both of the polishing head 106 and thebasin assembly 152.

The basin assembly 152 generally includes a basin 102 having a substratesupport or carrier 116 disposed therein. The carrier 116 generallysupports the substrate 104 within the basin 102 during processing. Thebasin 102 is generally non-electrically conductive and can be a bowlshaped member made of a plastic such as fluoropolymers, TEFLON® polymers(e.g., polytetrafluoroethylene—PTFE), perfluoroalkoxy resin (PFA),polyethylene-based plastics (PE), sulfonated polyphenylether sulfones(PES), or other materials that are compatible or non-reactive withelectrolyte compositions that may be used in electroplating orelectropolishing. The basin 102 generally includes sidewalls 108 and abottom 110 that generally defines a container or electrolyte cell inwhich a conductive fluid such as the electrolyte can be confined. Thebottom 110 generally includes a drain 142 to facilitate removal offluids from the bottom of the basin 102, while the sidewalls 108generally include an outlet 140 to facilitate removal of excesselectrolyte from the basin 102 during processing.

The basin 102 may be stationary or be driven to provide at least aportion of a relative motion between the substrate 104 and the polishinghead 106. In the embodiment depicted in FIG. 1A, an optional shaft 112is coupled to the bottom 110 of the basin 102 and is coupled to a drivesystem (not shown) to provide the basin 102 with a rotary, orbital,sweep motion or a motion comprising combinations thereof, among othermotions. The shaft 112 additionally provides a conduit for ground leads144 and other control or supply lines to be routed into or out of thebasin 102. In embodiments wherein the basin 102 is rotated by the shaft112, the drain 142 may also be routed through the shaft 112.

A spacer 114 is disposed on the bottom 110 of the basin 102. The spacer114 is typically annular in form and is comprised of a materialcompatible with process chemistries. In one embodiment, the spacer 114is fabricated from the same material as the basin 102. The spacer 114may optionally be fabricated with the basin 102 as a single member froma unitary mass of material.

The carrier 116 is generally disposed in the basin 102 and supported bythe spacer 114. The carrier 116 is typically fabricated from adielectric material such as a polymer or a ceramic material. The carrier116 generally includes a first side 118 and a second side 120. The firstside 118 includes a flange 122 substantially circumscribing a projectingcenter section 124. The flange 122 is disposed on the spacer 114 andsupports the carrier 116 above the bottom 110 of the basin 102. Thecenter section 124 projects into the open area defined within the spacer114 to locate the carrier 116 within the basin 102 and prevent movementof the carrier 116 during processing.

The second side 120 of the carrier 116 includes a projecting supportsurface 126 that extends towards the top of the basin 102. The supportsurface 126 generally supports the substrate 104 during processing. Thesupport surface 126 includes at least one vacuum port 132 formed thereinand coupled to a vacuum passage 128 disposed through the carrier 116.The vacuum passage 128 is fluidly coupled through the shaft 112 to avacuum source 146. Vacuum, drawn through the vacuum port 132, retainsthe substrate 104 on the support surface 126 during processing.Optionally, the support surface 126 may include topography that enhancesthe distribution of vacuum between the substrate 104 and support surface126 so that the substrate 104 is uniformly pulled towards the carrier116.

A plurality of lift pins 154 (only one is shown for clarity) is disposedthrough respective holes formed through the carrier 116. A lift plate156 disposed between the carrier 116 and the chamber bottom 110 iscoupled to an actuator rod 158. The actuator rod 158 is routed throughthe shaft 112 to a lift mechanism (not shown). The lift mechanism may beactuated to move the rod 158 and lift plate 156 towards the carrier 116.The lift plate 156 contacts the pins 154 and causes the pins 154 toextend above the support surface 126 of the carrier 116, thus placingthe substrate 104 in a spaced-apart relation relative to the carrier 116that facilitates access to the substrate 104 by a substrate transferdevice (not shown).

An annular retaining ring 130 is generally disposed on the flange 122 ofthe carrier 116. The retaining ring 130 generally snugly circumscribesand extends above a plane of the support surface 126. The thickness ofthe retaining ring 130 is configured so that a top surface 136 of theretaining ring 130 is substantially co-planar (i.e., within about ±1mil) with the feature side 138 of the substrate 104 to be processed. Thesidewalls 108 generally extend above the retaining ring 130 to define aprocessing area 150. The outlet 140 is typically located in the sidewall108 near the elevation of the top surface 136 of the retaining ring 130to allow the removal of electrolyte from the processing area 150 duringor after processing. During processing, the outlet 140 is closed and thebasin 102 is substantially full of electrolyte.

The top surface 136 of the retaining ring 130 is typically fabricatedfrom a material that does not adversely affect the polishing head 106which may periodically contact the top surface 136. In one embodiment,the retaining ring 130 is fabricated from a material compatible withprocessing chemistries, for example, a thermoplastic such aspolyphenylene sulfide (PPS) among other polymers. The retaining ring 130may be grounded by the ground lead 144 that is routed out of the processcell 100 through the shaft 112. If the retaining ring 130 is athermoplastic or other dielectric, there is no need to ground it sinceit is an electrical insulator.

Alternatively, the ring 130 may be metallic to promote uniformity acrossthe wafer (particularly at the edge of the substrate). For example, anungrounded copper retaining ring 130 may be used that has the samepotential as the substrate during processing.

The polishing head 102 generally includes a pad 160, an optionalmembrane 162, a support disk 164 and a counter-electrode 166 coupled toa housing 168. The pad 160 is generally exposed at the bottom of thepolishing head 102 and contacts the substrate 104 and, in someembodiments, the retaining ring 130 during processing. The pad 160 mayhave one or more conductive elements formed therein. The membrane 162 issandwiched between the pad 160 and the support disk 164. Thecounter-electrode 166 is disposed between the support disk 164 and theinterior of the housing 168. The pad 160, membrane 162, disk 164 and thecounter-electrode 166 are permeable, perforated, or contain passagesformed therethrough that allow the electrolyte to flow into and out ofthe polishing head 102.

The polishing head 106 may be stationary or driven to provide at least aportion of the relative motion between the substrate 104 and thepolishing head 106. In the embodiment depicted in FIG. 1A, the housing168 is coupled to a drive system (not shown) by a column 170. The drivesystem moves the column 170 thereby providing the polishing head 106with a rotary, orbital, sweep motion or a motion comprising combinationsthereof, among other motions. The column 170 additionally provides aconduit for electrical leads and other control or supply lines to berouted into or out of the polishing head 106.

The housing 168 is generally fabricated from a rigid material compatiblewith process chemistries. The housing 168 generally includes a top 178which is coupled to the column 170 and sides 180 extending therefrom.The sides 180 typically are coupled to the support disk 164, enclosingthe counter-electrode 166 within the housing 168. A plurality of spacingmembers (not shown) generally extend from the top 178 into the interiorof the housing 168. The spacing members keep the counter-electrode 166in a spaced-apart relation relative to the top 178. The spacing membersgenerally support the counter-electrode 166 in an orientation parallelto the surface of the substrate 104. The spacing members are configuredto allow fluids to move laterally within the housing 168.

The counter-electrode 166 and the substrate 104 define a region betweenwhich electrical biases (e.g., potential differences) are established.The biases may be applied between the counter electrode 166 and the pad160 that is placed in contact with a material layer that is formed onthe substrate 104. The pad 160 may be at least partially conductive andmay act as an electrode in combination with the substrate 104 duringelectrochemical processes, such as an electrochemical mechanical platingprocess (ECMPP), which includes electrochemical deposition and chemicalmechanical polishing, or electrochemical dissolution. Thecounter-electrode 166 may be an anode or cathode depending upon thepositive bias (anode) or negative bias (cathode) applied between thecounter-electrode 166 and the pad 160.

For example, when depositing material from an electrolyte onto thesubstrate surface, the counter-electrode 166 acts as an anode and thesubstrate surface and/or the pad 160 acts as a cathode. A reaction takesplace at the cathode causing material to deposit on the substratesurface. When removing material from a substrate surface, thecounter-electrode 166 functions as a cathode and the substrate surfaceand/or conductive pad 160 acts as an anode. The removal may result frommaterial on the substrate surface dissolving into the surroundingelectrolyte due to the application of the electrical bias.

The electrolyte within the basin 102 is maintained at a level thatensures that the lower surface of the counter-electrode 166 is immersedin the electrolyte during processing. The counter-electrode 166 ispermeable to the electrolyte and gases, and can be a plate-like member,a plate having multiple holes formed therethrough or a plurality ofcounter-electrode pieces disposed in a permeable membrane or container.

The counter-electrode 166 typically is comprised of the material to bedeposited or removed, such as copper, aluminum, gold, silver, tungstenand other materials which can be electrochemically deposited on thesubstrate 104. For electrochemical removal processes, such as anodicdissolution, the counter-electrode 166 may include a non-consumableelectrode of a material other than the deposited material, such asplatinum for copper dissolution. The non-consumable electrode is used inplanarization processes combining both electrochemical deposition andremoval.

FIG. 2 shows a bottom view of a counter-electrode 166 consistent withembodiments of the invention described herein. The counter-electrode hasa surface 890 that generally is positioned to face the surface 138 ofthe material layer 105 to be polished. The counter-electrode 166 may becharacterized as having a plurality of distinct zones. Three zones, anouter zone 824, an intermediate zone 826, and an inner zone 828 areshown by way of example in FIG. 2 (the zones 824, 826, 828 are separatedby zone boundaries 880 that are shown in phantom in FIG. 2).

Each zone of the counter-electrode 166 generally comprises at least oneconductive element (three conductive elements 850, 852, 854 are shown byway of example in FIG. 2) that is electrically isolated from theconductive elements in the other zones. Each conductive element may be,for example, a ring or a radially-oriented conductive element.Alternatively, other shapes and orientations, such as linear, curved,concentric, involute curves or other shapes and orientations arepossible for the conductive elements. The conductive elements may be ofsubstantially equal sizes and shapes from one zone to the next, or thesizes and shapes may vary depending upon the particular zone of concern.So that the zones may be separately biased, the conductive elements areseparated by insulating material such as a solid, liquid, or gaseous(e.g., air) dielectric material, or combinations thereof. The counterelectrode 166 may have perforations 860 therethrough to facilitate theflow of electrolyte through the counter-electrode 166.

Referring again to FIG. 1A, the support disk 164 is perforated orpermeable to the electrolyte and gases. The support disk 164 is madefrom a material compatible with the electrolyte that would notdetrimentally affect polishing. The support disk 164 may be fabricatedfrom a non-electrically conductive polymer, for example fluoropolymers,TEFLON® polymers (e.g., polytetrafluoroethylene—PTFE), perfluoroalkoxyresin (PFA), polyethylene-based plastics (PE), sulfonatedpolyphenylether sulfones (PES), high density polyethylene (HDPE),ultra-high molecular weight (UHMW) polyethylene, or other materials thatare compatible or non-reactive with electrolyte compositions that may beused in electroplating or electropolishing. The support disk 164 istypically secured in the housing 168 of the polishing head 106 usingadhesives, fasteners or other devices or methods that substantiallyensure the parallelism of the support disk 164 and the carrier 116. Thesupport disk 164 may be spaced from the counter-electrode 166 to providea wider process window, thus reducing the sensitivity of depositingmaterial and removing material from the substrate surface to thecounter-electrode 166 dimensions.

In one embodiment, the support disk 164 includes a plurality ofperforations or channels (not shown) formed therein. The size anddensity of the channels are selected to provide uniform distribution ofthe electrolyte through the support disk 164 to the substrate 104. Inone aspect, the support disk 164 includes channels having a diameterbetween about 0.5 mm and about 10 mm. The channels may have a densitybetween about 30% and about 80% of an area of the support disk 164 thatfaces the substrate 104. A channel density of about 50% has beenobserved to provide electrolyte flow with minimal detrimental effects topolishing processes. Generally, the channels of the support disk 164 andthe pad 160 may be aligned to provide for sufficient mass flow ofelectrolyte through the support disk 164 and the pad 160 to thesubstrate surface.

To facilitate control of polishing uniformity, a microprocessorcontroller 194, as shown in FIG. 1A may be electrically coupled to thevarious components of the process cell 100. The controller 194 comprisesa central processing unit (CPU) 244, a memory 242, and support circuits246 for the CPU 244. The CPU 244 may be one of any form of generalpurpose computer processor that can be used in an industrial setting forcontrolling various process equipment and sub-processors. The memory 242is coupled to the CPU 244. The memory 242, or computer-readable medium,may be one or more of readily available memory such as random accessmemory (RAM), read only memory (ROM), floppy disk, hard disk, or anyother form of digital storage, local or remote. The support circuits 246are coupled to the CPU 244 for supporting the processor in aconventional manner. These circuits include cache, power supplies, clockcircuits, input/output circuitry and subsystems, and the like. Apolishing process is generally stored in the memory 242 as a softwareroutine. The software routine may also be stored and/or executed by asecond CPU (not shown) that is remotely located from the hardware beingcontrolled by the CPU 244.

The software routine is executed after the substrate is positioned inthe process cell 100. The software routine when executed by the CPU 244,transforms the general purpose computer into a specific purpose computer(controller) 194 that controls the chamber operation such that theetching process is performed. Although the process of the presentinvention is discussed as being implemented as a software routine, someof the method steps that are disclosed therein may be performed inhardware as well as by the software controller 194. As such, theinvention may be implemented in software as executed upon a computersystem, in hardware as an application specific integrated circuit orother type of hardware implementation, or a combination of software andhardware.

The membrane 162 is generally permeable, thereby allowing the electricfield lines, electrolyte and other liquids and gases to passtherethrough. The membrane 162 generally prevents particles or sludgereleased from the counter-electrode 166 from passing through theelectrolyte and contacting the substrate 104. The membrane 162 istypically fabricated from a porous ceramic or polymer that is compatiblewith process chemistries and does not increase the cell resistance. Forexample, a spun-bonded polyolefin (such as TYVEK®, available from E. I.DuPont de Nemours, Inc., of Wilmington, Del.) may be used.

The pad 160 can be a pad, a web or a belt of material, which iscompatible with the fluid environment and the processing specifications.In the embodiment depicted in FIG. 1A, the pad 160 is circular in formand is adhered or otherwise retained to the membrane 162 at the bottomof the polishing head 106 opposite the housing 168 of the polishing head106. The pad 160 may include one or more conductive elements (not shownin FIG. 1A) for contacting the feature side 138 of the material layer105 during processing. A backing material (not shown) may be disposedbetween the membrane 162 and the pad 160 to tailor the compliance and/ordurometer of the pad 160 during processing. Examples of a conductive padthat may be adapted to benefit from the invention are disclosed in U.S.Ser. No. 10/033,732, filed Dec. 27, 2001, and issued as U.S. Pat. No.7,066,800, which paragraphs 41-157, as filed, which are hereinincorporated by reference to the extent not inconsistent with theclaimed aspects and description herein.

FIG. 3 depicts a bottom perspective view of one embodiment of a pad 400that may be used to practice embodiments described herein. The pad 400is a conductive pad comprising a body 406 having a polishing surface 402adapted to contact the substrate while processing. The polishing surface402 has a plurality of conductive elements 414, each of which may beformed within a pocket 404 within the polishing surface 402. Theconductive elements 414 generally have a contact surface 408 thatextends above a plane defined by the polishing surface 402. The contactsurface 408 is typically compliant to maximize electrical contact withthe substrate without scratching. During polishing, the substrategenerally provides a bias force that urges the contact surface 408 intoa position co-planar with the polishing surface 402.

The body 406 is generally permeable to the electrolyte by a plurality ofperforations 410 such as channels or apertures formed therein. Theplurality of perforations 410 allow electrolyte to flow through the body406 and contact the surface of the substrate during processing. Theperforations 410 formed in the conductive pad 400 may include apertures,channels, or holes in the body 406. The aperture size and density isselected to provide uniform distribution of electrolyte, as well ascurrent distribution, through the conductive pad 400 to a substratesurface.

The body 406 of the conductive pad 400 is generally made of a dielectricmaterial. Examples of materials suitable for use in the body 406 includeconventional polishing materials typically comprised of polymericmaterials, such as polyurethane, polycarbonate, polyphenylene sulfide(PPS), or combinations thereof, and other polishing materials, such asceramic material, used in polishing substrate surfaces. A conventionalpolishing media typically comprises polyurethane and/or polyurethanemixed with fillers. Conventional polishing media that may be usedincludes the Freudenberg FX 9 pad, which is commercially available fromFreudenberg & Company of Weinheim, Germany or the IC-1000 pad,commercially available from Rodel, Inc., of Phoenix, Ariz. Otherconventional polishing materials, such as a layer of compressiblematerial, for example felt leeched in urethane as in a Suba IV polishingpad commercially available from Rodel, Inc., of Phoenix, Ariz., may alsobe utilized for the body 406.

The pockets 404 generally are configured to retain the conductiveelements 414 while processing, and accordingly may vary in shape andorientation. In the embodiment depicted in FIG. 5, the pockets 404 aregrooves of rectangular cross section and are disposed across thepolishing surface 402 coupling two points on the perimeter of theconductive pad 160. Alternatively, the pockets 404 (and conductiveelements 414 disposed therein) may be disposed at irregular intervals,be orientated radially, perpendicular and may additionally be linear,curved, concentric, involute curves or other orientation.

Typically, the conductive elements 414 may include conductive polymers,polymer composites with conductive materials, conductive metals orpolymers, conductive fillers, graphitic materials, or conductive dopingmaterials, or combinations thereof. The conductive elements 414generally have a bulk resistivity or a bulk surface resistivity of about10 Ω-cm or less.

The pad 400 may be characterized as having a plurality of distinct zonessuch as an outer zone 424, an intermediate zone 426, and an inner zone428. The zones may correspond in shape and size to the zones of thecounter-electrode 166. Each zone may comprise at least one conductiveelement 414. The zones 424 may have linear boundaries 430, as depictedin FIG. 2. Alternatively, the zones 424 may have radial boundaries 430,or boundaries 430 with other geometries.

One or more connectors 412 couple the conductive elements 414 to thepotentiostat or power source 190 to electrically bias the conductiveelements 414 while processing. Each zone may have at least one connector412 in communication with the power source 190. The connectors 412 aregenerally wires, tapes or other conductors compatible with processfluids or having a covering or coating that protects the connector 412from the process fluids. The connectors 412 may be coupled to theconductive elements 414 by soldering, stacking, brazing, clamping,crimping, riveting, fastening, conductive adhesive or by other methodsor devices. Examples of materials that may be utilized in the connectors412 include insulated copper, graphite, titanium, platinum, gold, andHASTELLOY® among other materials. The connectors 412 may be coated with,for example, a polymer. In the embodiment depicted in FIG. 3, oneconnector 412 is coupled to each conductive element 414 at the perimeterof the conductive pad 400. Alternatively, the connectors 412 may bedisposed through the body 406 of the conductive pad 400.

To facilitate control of polishing uniformity, the microprocessorcontroller 194, as shown in FIG. 1A may be electrically coupled to thecounter-electrode 166 and the pad 160. Software routines may be used toprecisely control biases that are applied between the counter electrode166 and the substrate 104 and/or the pad 160.

While the polishing apparatus described above in FIG. 1A depicts a“face-up” polishing apparatus, it is also within the scope of theinvention to use a face-down polishing apparatus in which a substrate issupported face down above a polishing pad.

FIG. 1B depicts a sectional view of one embodiment of a “face-down”process cell 200. The process cell 200 generally includes a basin 204and a polishing head 202. A substrate 208 is retained in the polishinghead 202 and lowered into the basin 204 during processing in a face-down(e.g., backside up) orientation. An electrolyte is flowed into the basin204 and in contact with the substrate surface while the polishing head202 places the substrate 208 in contact with a pad assembly 222. Thesubstrate 208 and the pad assembly 222 disposed in the basin 204 aremoved relative to each other to provide a polishing motion (or motionthat enhances plating uniformity). The polishing motion generallycomprises at least one motion defined by an orbital, rotary, linear orcurvilinear motion, or combinations thereof, among other motions. Thepolishing motion may be achieved by moving either or both of thepolishing heads 202 and the basin 204. The polishing head 202 may bestationary or driven to provide at least a portion of the relativemotion between the basin 204 and the substrate 208 held by the polishinghead 202. In the embodiment depicted in FIG. 1B, the polishing head 202is coupled to a drive system 210. The drive system 210 moves thepolishing head 202 with at least a rotary, orbital, sweep motion orcombinations thereof.

The polishing head 202 generally retains the substrate 208 duringprocessing. In one embodiment, the polishing head 202 includes a housing214 enclosing a bladder 216. The bladder 216 may be deflated whencontacting the substrate to create a vacuum therebetween, thus securingthe substrate to the polishing head 202. The bladder 216 mayadditionally be inflated to press the substrate in contact with the padassembly 222 retained in the basin 204. A retaining ring 238 is coupledto the housing 214 and circumscribes the substrate 208 to prevent thesubstrate from slipping out from the polishing head 202 whileprocessing. One polishing head that may be adapted to benefit from theinvention is a TITAN HEAD™ carrier head available from AppliedMaterials, Inc., located in Santa Clara, Calif. Another example of apolishing head that may be adapted to benefit from the invention isdescribed in U.S. Pat. No. 6,159,079, issued Dec. 12, 2001, which isincorporated herein by reference in its entirety.

The basin 204 is generally fabricated from a plastic such asfluoropolymers, TEFLON® polymers (e.g., polytetrafluoroethylene—PTFE),perfluoroalkoxy resin (PFA), polyethylene-based plastics (PE),sulfonated polyphenylether sulfones (PES), or other materials that arecompatible or non-reactive with electrolyte compositions that may beused in electroplating or electropolishing. The basin 204 includes abottom 244 and sidewalls 246 that define a container that houses the padassembly 222.

The sidewalls 246 include a port 218 formed there through to allowremoval of electrolyte from the basin 204. The port 218 is coupled to avalve 220 to selectively drain or retain the electrolyte in the basin204.

The basin 204 is rotationally supported above a base 206 by bearings234. A drive system 236 is coupled to the basin 204 and rotates thebasin 204 during processing. A catch basin 228 is disposed on the base206 and circumscribes the basin 204 to collect processing fluids, suchas an electrolyte, that flow out of port 218 disposed through the basin204 during and/or after processing.

An electrolyte delivery system 232 is generally disposed adjacent thebasin 204. The electrolyte delivery system 232 includes a nozzle oroutlet 230 coupled to an electrolyte source 242. The outlet 230 flowselectrolyte or other processing fluid from the electrolyte source 242 tointo the basin 204. During processing, the electrolyte generallyprovides an electrical path for biasing the substrate 208 and driving anelectrochemical process to remove and/or deposit material on thesubstrate 208. Alternatively, the electrolyte delivery system mayprovide electrolyte through the bottom 244 of the process cell and flowelectrolyte through the pad assembly, including the dielectric insert207, to contact the polishing pad and substrate.

A conditioning device 250 may be provided proximate the basin 204 toperiodically condition or regenerate the pad assembly 222. Typically,the conditioning device 250 includes an arm 252 coupled to a stanchion254 that is adapted to position and sweep a conditioning element 258across pad assembly 222. The conditioning element 258 is coupled to thearm 252 by a shaft 256 to allow clearance between the arm 252 andsidewalls 246 of the basin 204 while the conditioning element 258 islowered to contact the pad assembly 222. The conditioning element 258 istypically a diamond or silicon carbide disk, which may be patterned toenhance working the surface of the pad assembly 222 into a predeterminedsurface condition/state that enhances process uniformity. Oneconditioning element 258 that may be adapted to benefit from theinvention is described in U.S. Ser. No. 09/676,280, filed Sep. 28, 2000,by Li et al., which is incorporated herein by reference to the extentnot inconsistent with the claimed aspects and description herein.

A power source 224 is coupled to the pad assembly 222 by electricalleads 212 (shown as 212A-B). The power source 224 applies an electricalbias to the pad assembly 222 to drive an electrochemical process asdescribed further below. The leads 212 are routed through a slip ring226 disposed below the basin 204. The slip ring 226 facilitatescontinuous electrical connection between the power source 224 and thepad assembly 222 as the basin 204 rotates. The leads 212 typically arewires, tapes or other conductors compatible with process fluids orhaving a covering or coating that protects the leads 212 from theprocess fluids. Examples of materials that may be utilized in the leads212 include insulated copper, graphite, titanium, platinum, gold, andHASTELLOY® materials among other materials. Coatings disposed around theleads 212 may include polymers such as fluorocarbons, PVC, polyamide,and the like.

As the pad assembly 222 includes elements comprising both an anode andcathode of an electrochemical cell, both the anode and cathode may bereplaced simultaneously by simply removing a used pad assembly 222 fromthe basin 204 and inserting a new pad assembly 222 with fresh electricalcomponents into the basin 204.

The pad assembly 222 depicted includes a conductive pad 203 coupled to abacking 205. The backing 205 may be coupled to an electrode 209.Typically, the conductive pad 203, the backing 205, and the electrode209 are secured together forming a unitary body that facilitates removaland replacement of the pad assembly 222 from the basin 204. Typically,the conductive pad 203, the backing 205, and the electrode 209 areadhered or bonded to one another. Alternatively, the conductive pad 203,the backing 205, and the electrode 209 may be coupled by other methodsor combination thereof, including sewing, binding, heat staking,riveting, screwing, and clamping among others.

The face-down polishing apparatus is more fully disclosed in commonlyassigned U.S. Ser. No. 10/151,538, filed May 16, 2002, and published asUS 2003-0213703, and which paragraphs 25-81, as filed, are incorporatedherein by reference to the extent not inconsistent with the claimedaspects and description herein. Similarly to face-up polishing, relativemotion is provided between the substrate and the electrode and/or pad.

Method of Polishing

Using embodiments described herein, the polishing uniformity of an ECMPprocess may be improved by selectively applying an electrical bias toindividual zones of a counter-electrode. Referring to FIG. 1A, thesubstrate 104 is transferred to the support surface 126 of the carrier116 in a typical lift pin assisted transfer operation. The polishinghead 106 is lowered into the basin 102 to place the substrate 104 incontact with the pad 160 or at least proximate thereto. Electrolyte issupplied to the basin 102 and to a level such that the electrolyte maycontact the counter-electrode 166, and the pad 160.

The electrolyte used in processing the substrate 104 can include metalssuch as copper, aluminum, tungsten, gold, silver, or other materialsthat can be electrochemically deposited onto or electrochemicallyremoved from the substrate 104. Electrolyte solutions may includecommercially available electrolytes. For example, in copper containingmaterial removal, the electrolyte may include between about 2 and about30% by volume or weight of sulfuric acid based electrolytes orphosphoric acid based electrolytes, such as potassium phosphate (K₃PO₄),phosphoric acid, or combinations thereof. Additionally, the inventioncontemplates using electrolyte compositions conventionally used inelectroplating or electropolishing processes.

The electrolyte may comprise one or more chelating agents, one or morecorrosion inhibitors, and one or more pH adjusting agents. The chelatingagents may include one or more groups selected from the group consistingof amine groups, amide groups, carboxylate groups, dicarboxylate groups,tri-carboxylate groups, and combinations thereof, for example,ethylenediamine. The chelating agents may be present in a concentrationbetween about 0.1% and about 15% by volume or weight.

The one or more corrosion inhibitors may include an organic compoundhaving azole groups, including benzotriazole, mercaptobenzotriazole, and5-methyl-1-benzotriazole. The electrolyte composition may includebetween about 0.01% and about 2.0% by volume or weight of the organiccompound having azole groups.

The pH adjusting agents that may be an acid, for example, acetic acid,citric acid, oxalic acid, phosphate-containing components, a base, suchas potassium hydroxide (KOH), or combinations thereof, to provide a pHbetween about 3 and about 10. The electrolyte composition may include,for example, between about 0.2% and about 25% by volume or weight of theone or more pH adjusting agents. The composition may further comprise upto 15% one or more additives selected from the following group:suppressors, enhancers, levelers, inhibitors, brighteners, chelatingagents, and stripping agents. An example of a suitable electrolyte ismore fully described in U.S. Ser. No. 10/032,275, filed Dec. 21, 2001,and issued as U.S. Pat. No. 6,899,804, which paragraphs 14-40, as filed,are incorporated herein by reference to the extent not inconsistent withthe claimed aspects and description herein.

The electrolyte flow rate is typically constant, for example betweenabout 0.1 gallons per minute (GPM) and about 20 GPM, but may varyaccording to the desires of the operator. Additionally, the inventioncontemplates that the electrolyte may be introduced from multiple inletsto provide variable electrolyte flow rates over portions of thesubstrate surface.

FIG. 4 is a sectional view of the process cell 100 that may be used topractice a polishing method consistent with embodiments of the inventiondescribed herein. Referring to FIG. 4 and to FIG. 1A, the substrate 104disposed on the substrate support 122 and the pad 160 may be moved(e.g., rotated, translated, orbited, etc.) relative to one another topolish the surface 138 of the substrate 104. The counter electrode 166is generally moved along with the pad 160. The counter electrode 166comprises a plurality of zones. An outer zone 1014, an intermediate zone1016, and an inner zone 1018 are shown by way of example in FIG. 4. Thecounter-electrode 166 has optional perforations 1010 formedtherethrough. The counter-electrode 166 is positioned, for example,proximate to the pad 160 during polishing.

Power from the potentiostat or power source 190 may be applied to thepad 160 and the counter-electrode 166 through electrical leads toprovide a bias therebetween. Three leads 192 a, 192 b, 192 c connectedto the respective zones 1014, 1016, 1018 of the counter electrode 166and the power source 190 are shown by way of example in FIG. 4. A lead199 is connected to the pad 160 through one or more conductive elements1088 formed in the pad 160. Each conductive element may have anindividual lead and a series of conductive elements may be connected tothe same lead as desired by the operator. The one or more conductiveelements 1088 may have a surface that is substantially coplanar with apolishing surface 1098 of the pad 160. While the description herein forthe power source 190 indicates one power source, the inventioncontemplates that a plurality of power sources may be used including anindividual power source for each lead or conductive element in theprocessing cell 100, 200.

The polishing motion may be applied before, after, or simultaneouslywith the application of the electrical bias. When contacting the surface138 of the substrate 104, the pad 160 typically applies a pressure ofabout 2 psi or less, such as between about 0.01 psi and about 0.5 psi,for example, about 0.2 psi, to the substrate surface. The relativemotion between the pad 160 and the substrate 104 may include rotational,linear or curvilinear motion, orbital motion or combinations thereof,among other motions.

In anodic dissolution, the bias may be applied to the counter-electrode166, performing as a cathode, and the substrate 104 (as well as theconductive pad, for embodiments in which a conductive pad is used)performing as the anode. The application of the bias allows removal ofdeposited material from the substrate surface. In an exemplary polishingprocess, a first bias, V1 is applied via the potentiostat or powersource 190 between the outer zone 1014 of the counter-electrode 166,performing as a cathode, and the pad 160, performing as the anode.Similarly, a second bias, V2 is applied between the intermediate zone1016 of the counter-electrode 166 and the pad 160. A third bias, V3 isapplied between the inner zone 1018 of the counter-electrode 166 and thepad 160. The application of the first bias V1, the second bias V2, andthe third bias V3 urges removal of material from the surface 138 of amaterial layer. Each bias V1, V2, and V3, may include the application ofa voltage of about 10 volts or less to the surface 138 of the substrate104.

Generally the bias is applied to provide a current density between about0.1 milliamps/cm² and about 50 milliamps/cm², or between about 0.1 ampsto about 20 amps for a 200 mm substrate. By varying the bias appliedbetween each zone of the counter electrode 166 and the substrate 104,the rate of material removal from the substrate surface 138 may bevaried. For example, a bias of a voltage of about 15 volts or less, suchas between 1 volt and 15 volts, including between about 2 and about 6volts, to a surface of the substrate 104 may be used with the processesdescribed herein for 200 mm and 300 mm substrates. Additionally, eachbias may be zero or “off” for a portion or all of a planarizing process.Further, the voltages described herein may be the voltages applied priorto any mechanical polishing and may be the voltages applied duringmechanical polishing as described as follows.

To facilitate the selection of appropriate values for V1, V2, and V3, arelationship between a rate of removal of material from the substratesurface 138 to be polished and a bias applied between thecounter-electrode 166 and the substrate surface is utilized. Therelationship may be a mathematical or statistical relationship such as afunctional relationship.

The relationship between removal rate and bias may be determinedempirically, for example, by polishing a plurality of test materiallayers 105 using a process cell such as the process cell 100. The testmaterial layers 105 may be polished according to a specific set ofinstructions that is communicated via software to the controller 194.The controller 194 relays the set of instructions to components of theprocess cell 100. The set of instructions may comprise providingrelative motion between the pad 160 and the substrate 104. The relativemotion may be, for example, linear, rotational, orbital, or combinationsthereof. A test bias, V_(t) is applied between the test material layer105 and the counter electrode 166. The test bias, V_(t), may be appliedsuch that a substantially uniform potential is generated across thecounter electrode 166 with respect to the surface 138 to be polished.The bias may be applied to the test material layer 105 using, forexample, a pad such as the pad 160 described above.

For example, referring to FIG. 5A, a top perspective view of a substrate604 shows a first test material layer 605 formed thereon. Similarly,FIG. 5B shows a second substrate 704 having a second test material layer705 formed thereon. The first test material layer 605 is polished byapplying a first test bias such as a uniform test bias across the testmaterial layer 605 relative to the counter electrode 166.

After polishing the test material layer 605 for a pre-determined periodof time (a first polishing time), the substrate 604 is, for example,removed from the process cell 100 and an amount of material removed fromthe test material layer 605 is then measured. The amount of materialremoved may be determined, for example, using conventional methods ofmeasuring layer thicknesses, such as sheet resistance (Rs) measurements.Alternatively, the amount of material removed may be measured usingelectron microscopy, or similar methods for analyzing thickness andcomposition of material layers. The material removal may be determinedby measuring a thickness 680 of the test material layer 605 beforepolishing and the thickness 680 after polishing. The thickness 680 maybe measured at a first point 620. Additional thickness measurements ofthe first test material layer 605 may be taken at one or more additionalpoints 622 in order to obtain a statistically representative value formaterial removal. Alternatively, a property other than thickness may bemeasured. For example, a mass of material removed or a material removalrate may be measured directly or indirectly. The one or more additionalpoints 622 on the test material layer 605 may be chosen such that thepoints lie within a region or zone of the test material layer 605 thatexperiences a relatively uniform rate of polishing (material removal).For example, the first point 620 and the additional points 622 may bechosen such that they all lie in an intermediate region 616 of the testmaterial layer 605. Alternatively, the first point 620 and theadditional points 622 may be chosen such that they each are a distancefrom a center 630 of the test material layer 605 that is substantiallythe same. A first rate of material removal may be determined by, forexample, dividing mass or thickness of the material removed by the firstpolishing time.

The second test material layer 705 may be polished using the samegeometry and configuration of the cell 100 as for the polishing of thefirst test material layer 605. The second test material layer 705 may bepolished by applying a second bias applied to the second test materiallayer 705. Thereafter, the step of determining material removal may beperformed for one or more points 720 on the second test material layer705. Furthermore, the process of determining removal rate may berepeated for additional test material layers (not shown), if desired.

The one or more points 720 on the test material layer 705 may lie withina region such as an intermediate region 716 of the material layer 105.The intermediate region 716 may have a similar shape and define asimilar range of distances from a center 730 of the material layer 705as is defined by the intermediate region 616 with respect to the center630.

By matching the material removal from each test material layer 605, 705with the corresponding bias applied to the test material layer, arelationship, such as a mathematical relationship between rate ofmaterial removal and bias may be determined. The relationship thusdetermined may be relevant for a specific configuration of the processcell 100, including a specific polishing composition as well as specificcomposition of material layer. Therefore, the relationship betweenmaterial removal and bias may be used to determine optimal bias voltagesto be applied when polishing a material layer using a process cell thathas a similar geometry/polishing composition to the process cell 100used to polish the test material layers 605, 705. The relationship maybe a linear relationship, an exponential relationship, or othermathematical relationship as determined between the rate of materialremoval and any applied bias. The mathematical relationship may also bemodified or adjusted to compensate for any effects of the type, shape,geometry, or limitations of the processing cell on the processes beingperformed therein.

Referring again to FIG. 5, after determining the relationship betweenbias and rate of material removal, a set of biases V1, V2, V3 that maybe desirably applied between the zones 1014, 1016, 1018 of thecounter-electrode 166 and the material layer 105 are determined. The setof desirable biases V1, V2, V3 may be selected in order to generate apre-determined removal profile, i.e., generate a separate rate ofmaterial removal for different regions of the material layer 105. Forexample, FIG. 6A shows one example of a removal profile 900 that may bedesirably generated. The removal profile 900 is substantially uniformacross the material layer 105 to be polished (i.e., does not vary acrosssurface 138 of the material layer 105, such as, for example, vary with adistance from a center such as the center 630 of the test material layer105 shown in FIG. 4A).

In an alternative embodiment of the invention, as shown in FIG. 6B, theset of biases V1, V2, V3 are selected to generate a removal profile 902that varies across the surface 138 to be polished. The alternativeembodiment depicted in FIG. 6B, may be employed, for example, in casesin which the surface 138 of the substrate 104 and/or material layer 105is irregular (e.g., either the substrate 104 or the material layer 105is bowed, warped, uneven, not flat, or otherwise has a variablethickness). For example, FIG. 7 shows a cross-sectional view of thesubstrate 104 having a material layer 1105 formed thereon, wherein thematerial layer 1105 has a thickness 1180 that varies substantiallyacross the surface 1138 to be polished). By applying biases thatgenerate the non-uniform removal profile 902, material can be removedmore rapidly from, for example, an edge region 1124 of the materiallayer 1105 than for a center region 1128.

For a known set of biases, V1, V2, V3 applied to zones of thecounter-electrode 166, a corresponding set of removal rates, R1, R2, R3,can be estimated, calculated, or modeled using the pre-determinedrelationship, between applied bias and removal rate. The removal ratesR1, R2, R3, associated with the zones of the counter-electrode 166 canbe used to determine removal rates that will be experienced by thematerial layer to be polished. Optimal values for biases V1, V2, V3 canbe determined using techniques described below.

The material layer 105 is polished, for example, by providing apre-determined set of instructions to the components of the process cell100 using the controller 194. The predetermined set of instructionsdefines a specific sequence of relative motion between the pad 160 andthe substrate 104. Using an appropriate algorithm, the location of anypoint on the material layer 105 as a function of time relative to thepad 160 can be calculated. Furthermore, the amount of time that anypoint on the material layer 105 is associated with each zone of thecounter electrode 166 may also be determined by the algorithm. Becauseeach zone of the pad 160 has a removal rate that is a function of thebias applied to that zone, it can therefore be determined the amount oftime that any point on the material layer 105 is associated with eachremoval rate. The removal rate for any point on the material layer 105can then be calculated as, for example, as an average of the removalrates of each zone, wherein the average is weighted by the amount orfraction of time that the point on the material layer 105 spends in eachzone. In general, the material layer 105 may be polished in the processcell 100 used to polish the test material layers 605, 705.Alternatively, the material layer 105 may be polished in a process cellhaving similar geometry (e.g., substantially similar size and shape atthe counter-electrode 166, a substantially similar distance between thecounter-electrode 166 and the substrate 104, and the like).

Exemplary Polishing Method

A counter-electrode such as the counter-electrode 166 was divided intofive zones: an inner zone, an inner-central zone, a central zone, anouter-central zone and an outer zone (Z1, Z2, Z3, Z4, and Z5)respectively. The zones were arranged in a concentric circular mannersimilar to the zones depicted for the counter-electrode 166 shown inFIG. 2. Each of the zones was capable of receiving a separate bias withrespect to a material layer to be polished. One hundred twenty onepoints, representing a broad sampling of various locations on thematerial layer were selected. A pre-determined set of instructions(i.e., a polishing program) that encoded a sequence of relative motionbetween the counter-electrode 166 (as well as the pad 160) and thematerial layer 105 was provided to controller 194. An algorithm based onthe polishing program was used to determine the sequence of relativepositions between the material layer 105 and the counter-electrode 166as a function of time throughout the polishing process. The algorithmcalculated the location of each point relative to the five zones of thecounter-electrode 166 for each of a total of 2400 instants in time (timesteps). The algorithm also calculated the number of time steps eachpoint was associated with each of the five zones (e.g., the number oftimes the point would be facing or under each of the zones of thecounter-electrode 166). Note that for embodiments in which the processcell 100 comprises the pad 160, a point on the material layer 105 onlyexperiences a bias when the point on the material layer 105 is facing aperforation 410 in the pad 160. If the point is not facing a perforation410 in the pad 160, no bias will be experienced by the point on thematerial layer 105.

Based upon the program to be used to polish the material layer, thealgorithm determined that a first point in the center of the materiallayer was associated with Z2 for 1080 time steps (i.e., 45% of the totalnumber of time steps), associated with Z1, Z3, Z4, Z5 for 0 time steps,and associated with none of the zones (i.e., the point was not under aperforation 1010 in the pad and therefore zero bias was experienced bythe point) for the remaining 1320 time steps. Therefore, for 45% oftime, point A was associated with Z2, and the expected removal ratewould be 0.45×R2.

From the algorithm it was further determined that a second point B, awayfrom the center of the material layer) was associated with Z2 for 570time steps (or 23.75% of the total number of time steps), associatedwith Z3 for 774 time steps (or 32.35% of the total number of timesteps), and associated with no zones (i.e., not under a perforation inthe pad) for 1056 time steps. The expected removal rate for point B istherefore given by an average of the removal rates for Z1, Z2, Z3, Z4,and Z5, weighted by the percentage of the time spent in each zone.Expressed in mathematical terms, the expected removal rate for point Bis given by the mathematical expression, [0.2375×R2]+[0.3235×R3].

The algorithm further calculated the expected removal rate for theremainder of the 121 points on the material layer in a similar manner.Specifically, for each point an expected removal rate was calculated as[A1×R1]+[A2×R2]+[A3×R3]+[A4×R4]+[A5×R5]. A1, A2, A3, A4, and A5 are thepercentage of times that the particular point was associated with thezones Z1, Z2, Z3, Z4, and Z5 respectively.

The material layer to be polished had a non-uniform surface to bepolished. In order to compensate for the non-uniform surface 138, thedesired removal profile was similar to the removal profile 902, shown inFIG. 7B. A least-squares regression was performed to optimize the valuesfor R1, R2, R3, R4, and R5 such that the removal profile of the materiallayer 105 after polishing would closely match the desired removalprofile. The optimal biases to be applied to each of the zones were thendetermined using a pre-determined (linear) relationship between removalrate and bias (specifically bias in volts equal removal rate inthousands of Angstroms per minute). The results of the regression andthe assumption of the linear relationship between bias and removal rateyielded a value of V1 of 2.0222 volts, a value of V2 of 1.8569 volts avalue of V3 of 2.0028 volts, and a value of V4 of 3.7397 volts a valueof V5 of 6.7937 volts. The material layer 105 was polished using thesebiases and the resultant removal profile was similar to the desiredremoval profile.

While FIG. 5 depicts the use of the counter-electrode 166 that isdivided into three radial zones, each of which may be separately biasedwith respect to the material layer 105, other pad configurations arepossible. The counter-electrode 166 may be divided into zones of anynumber greater than one. Similarly, the zones of the counter-electrode166 need not be radial as depicted in FIG. 4. The zones may be may be ofany geometrical configuration, such as, for example, linear sections.

Furthermore, in addition to the counter-electrode 166, one or morereference electrodes may be used to apply the separate biases to thematerial layer 105. Examples of methods that may be used to apply aplurality of biases between one or more electrodes and a material layerto be polished are provided in commonly assigned U.S. Ser. No.10/244,697, filed Sep. 16, 2002, and issued as U.S. Pat. No. 6,991,526,which is herein incorporated by reference to the extent not inconsistentwith the claimed aspects and description herein.

While the method described above is discussed in the context of an ECMPprocess, the invention contemplates using the method in otherfabrication processes involving electrochemical activity. Examples ofsuch processes using electrochemical activity include electrochemicaldeposition, which involves a pad 160 being used to apply a uniform biasto a substrate surface for depositing a conductive material without theuse of a conventional bias application apparatus, such as edge contacts,and electrochemical mechanical plating processes (ECMPP) that include acombination of electrochemical deposition and chemical mechanicalpolishing.

While the foregoing is directed to various embodiments of the invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A pad assembly for electro-processing a substrate, comprising: afirst conductive layer having a working surface to contact a substrateduring a polishing process; an intermediate layer coupled to the firstconductive layer, wherein the intermediate layer comprises a pluralityof perforations, channels, or combinations thereof, and the perforationsor channels have diameters within a range from about 0.5 mm to about 10mm; and a second conductive layer coupled to the intermediate layer,wherein the second conductive layer has a plurality of independentlyelectrically biasable zones and is configured to be coupled with a powerdelivery arrangement.
 2. The pad assembly of claim 1, wherein the firstconductive layer, the second conductive layer, and the intermediatelayer are adhered or secured together and removable as a unitaryreplaceable body.
 3. The pad assembly of claim 1, wherein the firstconductive layer comprises a dielectric body and at least one conductiveelement.
 4. The pad assembly of claim 3, wherein the dielectric bodycomprises a polymeric material.
 5. The pad assembly of claim 4, whereinthe polymeric material is selected from the group consisting ofpolyurethane, polycarbonate, polyphenylene sulfide, polyethylene, andcombinations thereof.
 6. The pad assembly of claim 4, wherein thepolymeric material is a fluoropolymeric material.
 7. The pad assembly ofclaim 1, wherein the first conductive layer is at least one of permeableto electrolyte or contains perforations.
 8. The pad assembly of claim 1,wherein the first conductive layer further comprises a plurality ofconductive elements adapted to deliver a current to the working surface.9. The pad assembly of claim 8, wherein the first conductive layercomprises a dielectric body and the plurality of conductive elements areconfigured to be coupled with the power delivery arrangement.
 10. Thepad assembly of claim 1, wherein the working surface further comprisesat least one of grooves, embossment, or other texturing formed therein.11. The pad assembly of claim 1, further comprising at least one contactelement extending through the pad assembly and adapted to deliver acurrent to the working surface.
 12. The pad assembly of claim 1, whereinthe intermediate layer comprises a polymer material support disk, abacking layer, or combinations thereof.
 13. The pad assembly of claim 1,wherein the second conductive layer further comprises a plurality ofconcentric conductive elements.
 14. The pad assembly of claim 1, whereinthe second conductive layer further comprises conductive elementscomprising a material selected from the group consisting of copper,graphite, titanium, platinum, and gold.
 15. A pad assembly forelectro-processing a substrate, comprising: a first conductive layerhaving a working surface to contact a substrate, wherein the firstconductive layer comprises a dielectric body and at least one conductiveelement, and the dielectric body comprises a polymeric material selectedfrom the group consisting of polyurethane, polycarbonate, polyphenylenesulfide, polyethylene, fluoropolymeric material, and combinationsthereof; a second conductive layer having a plurality of independentlyelectrically biasable zones and is configured to be coupled with a powerdelivery arrangement; and an intermediate layer between and coupled withthe first conductive layer and the second conductive layer, wherein theintermediate layer comprises a polymer material support disk, a backinglayer, or a combination thereof.
 16. The pad assembly of claim 15,wherein the first conductive layer, the second conductive layer, and theintermediate layer are adhered or secured together and removable as aunitary replaceable body.
 17. The pad assembly of claim 15, wherein theintermediate layer comprises a plurality of perforations, channels, orcombinations thereof, and.
 18. The pad assembly of claim 17, wherein theperforations or channels have diameters within a range from about 0.5 mmto about 10 mm.
 19. The pad assembly of claim 15, wherein the firstconductive layer further comprises a plurality of conductive elementsadapted to deliver a current to the working surface.
 20. The padassembly of claim 19, wherein the conductive elements are configured tobe coupled with the power delivery arrangement.
 21. The pad assembly ofclaim 15, wherein the first conductive layer is at least one ofpermeable to electrolyte or contains perforations.
 22. The pad assemblyof claim 15, further comprising at least one contact element extendingthrough the pad assembly and adapted to deliver a current to the workingsurface.
 23. The pad assembly of claim 15, wherein the second conductivelayer further comprises a plurality of concentric conductive elements.24. The pad assembly of claim 15, wherein the second conductive layerfurther comprises conductive elements comprising a material selectedfrom the group consisting of copper, graphite, titanium, platinum, andgold.
 25. A method of processing a substrate surface, comprising:disposing a substrate having a conductive material layer formed thereonwithin a process apparatus comprising an electrode having a plurality ofzones and a polishing pad having a plurality of zones corresponding tothe plurality of zones of the electrode, wherein the polishing padfurther comprises: a first conductive layer having a working surface tocontact the substrate during a polishing process; an intermediate layercoupled to the first conductive layer; and a second conductive layercoupled to the intermediate layer; contacting the polishing pad and thesubstrate; providing relative motion between the polishing pad and thesubstrate; and separately applying a plurality of biases between theplurality of zones of the polishing pad and the plurality of zones ofthe electrode.